Title: Induced-Charge Electro-osmosis

Speaker: Martin Z. Bazant 
	 Department of Mathematics and
	 Institute for Soldier Nanotechnologies
	 MIT

Abstract:

``Induced-charge electro-osmosis'' (ICEO) refers to the nonlinear
electrokinetic slip at a polarizable surface when an electric field
acts on its own induced double-layer charge. Here, we develop a simple
physical picture of ICEO in the context of some new techniques for
microfluidic pumping and mixing. ICEO generalizes ``AC
electro-osmosis'' at micro-electrode arrays to various dielectric and
conducting structures in weak DC or AC electric fields. The basic
effect produces micro-vortices to enhance mixing in microfluidic
devices, while various broken symmetries --- controlled potential,
irregular shape, non-uniform surface properties, and field gradients
--- can be exploited to produce streaming flows with small AC
voltages. We also present new experiments demonstrating ICEO vortices
around platinum posts in polymer microchannels. Such devices may be
easily integrated into biomedical microfluidics to reduce
mixing times (e.g. for DNA hybridization assays).